Joe Cro N3IBX says his "big antenna" is resonant from 1500 kHz to 46
mHz.

It is a military inverted-V, 110 ft. long total, with each end
terminated in a 150 ohm resistor driven into the ground, center fed
through a 9:1 balun.

Assuming this is not an April 1 joke:

(1) What are the drawbacks to this antenna?

(2) What is the feedline?

(3) Is there any more information about this type of antenna?

(4) What is the point of burying the resistor, rather than one lead?

Ken KC2JDY

Ken
(to reply via email
remove "zz" from address)

I haven't read the article, but I expect the word 'resonant' is
incorrectly used.

Any antenna terminated with real resistors into the ground is generally
a traveling wave non resonant antenna.

In addition to radiating some of the RF it also wastes some of the RF in
the two load resistors.

It should work but not as well as a 110 foot inverted vee, open wire
feeders and a tuner.

Deacon Dave, W1MCE

Ken wrote:

Joe Cro N3IBX says his "big antenna" is resonant from 1500 kHz to 46
mHz.

It is a military inverted-V, 110 ft. long total, with each end
terminated in a 150 ohm resistor driven into the ground, center fed
through a 9:1 balun.

Assuming this is not an April 1 joke:

(1) What are the drawbacks to this antenna?

(2) What is the feedline?

(3) Is there any more information about this type of antenna?

(4) What is the point of burying the resistor, rather than one lead?

Ken KC2JDY

Ken
(to reply via email
remove "zz" from address)

Ken wrote:

Joe Cro N3IBX says his "big antenna" is resonant from 1500 kHz to 46
mHz.

He's defining "resonant" as no reflections. Instead of a
standing-wave antenna, he is sacrificing half his power
(or more) in the resistors to avoid reflections and turning
the antenna into a traveling-wave antenna.

It is a military inverted-V, 110 ft. long total, with each end
terminated in a 150 ohm resistor driven into the ground, center fed
through a 9:1 balun.

Assuming this is not an April 1 joke:

It's somewhat like a terminated-V antenna, described in the
ARRL Antenna Book.

(1) What are the drawbacks to this antenna?

He is losing at least half his power in the resistors.
Wouldn't you rather radiate that power? I go to great
lengths to obtain an extra 1 dB.

(2) What is the feedline?

With a 9:1 balun, it can be coax since there are so few
reflections.
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...

He is losing at least half his power in the resistors.
Wouldn't you rather radiate that power? I go to great
lengths to obtain an extra 1 dB.



If I remember my traveling wave antenna theory, he wouldn't necessarily be
loosing 3 dB in the resistors. At higher frequencies more of the power
radiates before it gets to the loads, does it not?

Jim
N8EE

On Thu, 15 Apr 2004 11:34:21 -0400, "JLB"
wrote:
If I remember my traveling wave antenna theory, he wouldn't necessarily be
loosing 3 dB in the resistors. At higher frequencies more of the power
radiates before it gets to the loads, does it not?

Jim
N8EE

Hi Jim,

You are right (losing - unless it has diarrhea). What is described is
a vertical, half Rhombic, a Military application for many years. This
report appears to be about a design from yet another "inventor" who
has "discovered" something that confounds the experts.

The original poster asked for comments, especially about the resistor
(the difference between shorting it and loading it) however, nothing
is said about ground. Both of the resistors will require radials,
however, there seem to be more specifics missing than that.

In other words, what is the leg angle subtended at the fed point? Why
not simply feed one end and terminate the other? Seems like a pain to
elevate the feed point without some analysis showing why - but then it
appears the column was painfully shy of anything technical beyond
carpenter scaling.

73's
Richard Clark, KB7QHC

JLB wrote:
"Cecil Moore" wrote:
He is losing at least half his power in the resistors.
Wouldn't you rather radiate that power? I go to great
lengths to obtain an extra 1 dB.

If I remember my traveling wave antenna theory, he wouldn't necessarily be
loosing 3 dB in the resistors. At higher frequencies more of the power
radiates before it gets to the loads, does it not?

Yes, "more" but not near 100%. A multi-wavelength terminated rhombic
loses its reverse radiated lobes and along with them, quite a bit
of power. Even on 10m, 110 ft. is only 3 wavelengths long. Averaged
over all of HF, I'll bet that antenna loses close to half of its power
in the resistors, assuming all reflections have been eliminated by
the resistors.
--
73, Cecil http://www.qsl.net/w5dxp

"Richard Clark" wrote in message
news
You are right (losing - unless it has diarrhea). What is described is
a vertical, half Rhombic, a Military application for many years. This
report appears to be about a design from yet another "inventor" who
has "discovered" something that confounds the experts.


Dick,

I challenge any antenna 'inventor' to invent an antenna that is not
described in Kraus' book, at least at the fundamental theory level! Haven't
seen one yet and I've been reading QST for over 30 years (not to mention my
dad's collection that goes back to 1942).

By the way, I 'invented' an interesting antenna several years ago, which I
call the half-quad. The best way to describe it is dto picture a diamond
shape quad, fed at the side corner, half buried in the ground. Shows some
interesting patterns on the good ol' AO program. I came up with a three
element version with one feed point (center element). You can change
directions by switching a capacitor or inductor in and out of the two
'outside' elements. It didn't use terminating resistors. I couldn't get a
multiband version to work. (and, no, I haven't built it yet)

Jim
N8EE
(and yes, I qualify for the OT club but don't want to admit it quite yet).

If I understand your description correctly, I'd be highly suspicious of
the results from AO or any other MININEC-based program because of the
antenna's relatively low height. I recommend that you model the antenna
with an NEC-2 based program using the Sommerfeld ground model (called
"high-accuracy" ground in EZNEC) -- otherwise you might be pretty
disappointed when you actually build it. Be sure to make note of the
strength of the pattern as well as the shape of the NEC-2 program
results, unless you're using the antenna only for receiving.

Roy Lewallen, W7EL

JLB wrote:
. . .
By the way, I 'invented' an interesting antenna several years ago, which I
call the half-quad. The best way to describe it is dto picture a diamond
shape quad, fed at the side corner, half buried in the ground. Shows some
interesting patterns on the good ol' AO program. I came up with a three
element version with one feed point (center element). You can change
directions by switching a capacitor or inductor in and out of the two
'outside' elements. It didn't use terminating resistors. I couldn't get a
multiband version to work. (and, no, I haven't built it yet)

Jim
N8EE
(and yes, I qualify for the OT club but don't want to admit it quite yet).

After investigating a large set of traveling wave antennas (not
Beverage) I think that the smallest amount of power dissipated in the
terminating resistance was about 2 db. Mind, these were antennas with
useful lengths and angles. It is likely that a rhombic with very long
leg lengths would dissipate even less in its termination resistance.
For amusement, I will have a look some time. One needs a lot of
segments to simulate a three wire, ten wavelength rhombic!
The antenna in question can be a useful expedient in exigent
circumstances.
Nice to hear from N8EE, another of Kraus' boys. 73 Mac N8TT
--
J. Mc Laughlin - Michigan USA
Home:

"JLB" wrote in message
...




If I remember my traveling wave antenna theory, he wouldn't
necessarily be
loosing 3 dB in the resistors. At higher frequencies more of the
power
radiates before it gets to the loads, does it not?

Jim
N8EE

J. McLaughlin wrote:
After investigating a large set of traveling wave antennas (not
Beverage) I think that the smallest amount of power dissipated in the
terminating resistance was about 2 db. Mind, these were antennas with
useful lengths and angles. It is likely that a rhombic with very long
leg lengths would dissipate even less in its termination resistance.

Well, remember the posting that kicked off this discussion was about
the following very short traveling-wave antenna:

"It is a military inverted-V, 110 ft. long total, with each end
terminated in a 150 ohm resistor driven into the ground, center fed
through a 9:1 balun."

A 110 ft. center-fed inverted-V is certainly going to have extensive
losses in the resistors on most HF bands. After all, it is less than
1/2WL long on 75m and only 3 wavelengths long on 10m.
--
73, Cecil, W5DXP



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